1997 Johnson Evinrude "EU" 40 thru 55 2-Cylinder Service Manual, P/N 507265, Page 309Get this manual
Modes of Operation UP
1When the UP button is pressed, the pump Q) rotates in counterclockwise direction2Fluid pressure opens the UP check valve and moves the pump control pistonmechanically opening the DOWN check valve 3Fluid pressure is directed to the bottom of the cylinder to move the piston UP4Low pressure fluid leaves the top of the cylinder, moves through the open DOWN check valveand returns to the pump Q)
5To allow for the volume differential caused by the piston rod, additional fluid is drawn into the pump the reservoir